def total():
    if os.path.exists(filename):
        with open(filename,'r') as rfile:
            student_old = rfile.readlines()
            if student_old:
                print("一共有 %d 个学生"% len(student_old))
            else:
                print("还没有录入学生信息")
    else:
        print("未保存数据信息")